Recursion: 4 ways to get it working

[TempodiBasic]

Hi
I think that this demo is clear enough to be used as example about recursion in QB64pe.

I must remark that the STATIC way has is goal in preserving the previouse values of variable of the SUB/FUNCTION.
So if we need to preserve  few variables we can use STATIC into the SUB to declare the variable to preserve,
instead if we need to preserve all variable or the more part  of local variables we use STATIC in SUB/FUNCTION declaration.

Code: (Select All)

Rem Demonstration of variables into recursive calling
Screen 0
Dim counter As Single
Dim Shared counter2 As Single
Dim Choice As String

Choice = " "
Do
    If Choice <> "" Then
        Cls
        Print "we are testing recursive calling"
        Print String$(60, "#")
        Print "please make your choice: "
        Print " press 1 for recursion without parameter or shared variable"
        Print " press 2 for recursion with parameter and no shared variable"
        Print " press 3 for recursion with shared variable and no parameter"
        Print " press 4 for STATIC recursion without parameter or shared variable"
        Print " press 0 to exit from demonstration"
        Print String$(60, "#")
    End If
    Choice = InKey$
    If Choice = "0" GoTo Ending
    If Choice = "1" Then GoSub NoParameters
    If Choice = "2" Then GoSub YesParameters
    If Choice = "3" Then GoSub SharedVariable
    If Choice = "4" Then GoSub StaticNoParameters
Loop
End

NoParameters:
counter = 0
Print " No parameter and no shared variable demo"
Print "-----------------------------------------"
Print counter; " value of flag in the main"
RecursiveNoParameters
Return

YesParameters:
counter = 0
Print " Yes parameter and no shared variable demo"
Print "------------------------------------------"
Print counter; " value of flag in the main"
RecursiveYesParameters counter
Return

SharedVariable:
counter2 = 0
Print " No parameter and Yes shared variable demo"
Print "------------------------------------------"
Print counter2; " value of flag in the main"
SharedVariables
Return

StaticNoParameters:
counter = 0
Print " STATIC and no parameter and no shared variable demo"
Print "-----------------------------------------"
Print counter; " value of flag in the main"
StaticNoParameter
Return

Ending:
Rem here the flow of code ends
End


Sub RecursiveNoParameters
    counter = counter + 1
    DoJob counter
    If InKey$ <> "" Then Exit Sub ' emergency exit
    If counter < 10 Then RecursiveNoParameters
End Sub

Sub RecursiveYesParameters (c As Single)
    c = c + 1
    DoJob c
    If InKey$ <> "" Then Exit Sub ' emergency exit
    If c < 10 Then RecursiveYesParameters c
End Sub

Sub SharedVariables
    counter2 = counter2 + 1
    DoJob counter2
    If InKey$ <> "" Then Exit Sub ' emergency exit
    If counter2 < 10 Then SharedVariables
End Sub

Sub StaticNoParameter
    Static counter ' you need to have STATIC only the flag of recursion, at least
    counter = counter + 1
    DoJob counter
    If InKey$ <> "" Then Exit Sub ' emergency exit
    If counter < 10 Then StaticNoParameter
End Sub


Sub DoJob (c As Single)
    Print c; " press a key to stop the recursive loop"
    Sleep 1 ' we need this to avoid the crash of application
End Sub

more explanation and tips coming soon.